Radio-Frequency Identification (RFID) technology has become widely used in virtually every industry, including transportation, manufacturing, waste management, postal tracking, airline baggage reconciliation, and highway toll management. A typical RFID system includes a plurality of RFID tags, at least one RFID reader or detection system having an antenna for communication with the RFID tags, and a computing device to control the RFID reader. The RFID reader includes a transmitter that may provide energy or information to the tags, and a receiver to receive identity and other information from the tags. The computing device processes the information obtained by the RFID reader.
A variety of RFID applications, systems and tags are known. For example, U.S. Patent Application Publication entitled, “Radio Frequency Identification in Document Management,” (Eisenberg et al.), Publication No. 2002/0196126 A1, discloses various systems and methods of handling items with RFID tags, such as files. As another example, PCT Publication WO 00/10122 A2, “Radio Frequency Identification Systems Applications,” (Garber, et al.) describes the use of RFID systems for use with items of interest having RFID tags, such as in a library. As yet another example, U.S. Pat. Ser. No. 6,768,419, “Applications for Radio Frequency Identification Systems” (Garber, et al.) describes RFID devices, including handheld RFID devices, and applications for such devices. Another example, U.S. Patent Publication No. 2003/0189490 A1, “Radio-Frequency Identification Tag and Tape Applicator, Radio-Frequency Identification Tag Applicator, and Methods of Applying Radio-Frequency Identification Tags” describes methods of applying a radio-frequency identification tag to tape and radio-frequency identification tag and tape applicators.
One example of RFID tags is described in U.S. patent application Ser. No. 10/820,584, entitled “Variable Frequency Radio Frequency Identification (RFID) Tags,” (Waldner and Erickson), which describes various radio frequency identification (RFID) tags that dynamically vary their resonant frequency to reduce or eliminate the potential effects of electromagnetic “tag-to-tag” coupling. Another example of RFID tags is described in U.S. patent application Ser. No. 10/807,072, “Radiofrequency Identification Tags with Compensating Circuitry.”